Turbine generators for producing electric power are well known. Turbine generators typically comprise an end winding portion that includes a stator core that defines several slots that receive and support conductors. The end windings, however, may not be adequately supported within the core slots during operation of the generator. Thus, the end windings may be subject to severe vibrations and stresses which may cause adverse structural deformations. Structural deformation may also arise from electromagnetic forces which occur during abnormal short-circuit or fault conditions.
Several methods have been developed in an attempt to prevent the end windings from undergoing negative structural deformations, such as the method shown in FIG. 1 which is disclosed in U.S. Pat. No. 4,563,607 to Cooper et al. and assigned to the assignee of the present invention. A top coil 10 and bottom coil 12 are disposed within slots 14 defined by a stator iron core 16. The coils 10 and 12 are supported with a radial clamp 18, braces 20, brackets 22, rings 24, 26, 28, 30 and strain blocks 32. The radial clamp 18 is positioned in the mid-involute region between the axial extreme of the end winding and the core.
FIG. 2 is a sectional view taken along section line 2--2 in FIG. 1. As shown, the support blocks 34 and 36 are located radially above and below a respective pair of end turns so that one support block 34 bears against two bottom coils 12a and 12b and the other support block 36 bears against two top coils 10a and 10b. Each one of the support blocks 34 and 36 is spaced from an adjacent coil by a layer 38 of conformable material.
A relative upper pin 40 is disposed across support block 36 transverse to the direction in which the coils run and a relative lower pin 42 is similarly disposed across support block 34. A tensioned banding loop 44 is disposed in a continuous loop around the pins 40 and 42 on each side of the coils so that the banding loop 44 bears against the pins which, in turn, bear against their adjacent support blocks and coils. A shim 46 is disposed between the pin 40 and the support block 36. Spring members 48 and support washers 50 are disposed between the lower pin 42 and support block 34.
The pins 40 and 42 are adapted to turn and twist the banding loop 44 to take in excess slack in the banding loop, thereby, tightening the banding loop 44 between the coils 10 and 12. The resin within the banding loop 44 is then cured, such as by hot air. After the banding loop 44 is positioned and cured, a device, such as a hydraulic jack, is used to pull at least one of the pins radially away from the coils, thereby, stretching and inducing a tension on the banding loop 44. Subsequently, the shims 46 are placed between the upper pin 40 and support block 36 so that the banding loop 44 remains in tension upon the release of the hydraulic jack.
The apparatus shown in FIGS. 1 and 2, as with other conventional apparatus, however, has several drawbacks. One such drawback is that the curing process requires additional time and expense to install, or extends schedules for band curing, and consequently adds to the overall cost of the turbine generator. It would, therefore, be desirable to provide a more economical means of installing and maintaining a turbine generator.
Another drawback is that additional time and generator components are required to adjust the banding loop. It would, therefore be desirable to reduce the number of components that must be accounted for during the installation of radial clamp bands.